One embodiment of a modular base assembly comprises a frame and leveler assemblies used to support a vehicle model. The frame has a frame segment with several parts including a cross-support and a side-support having a surface defining a plurality of holes where model-making components can be attached and unattached thereto. Leveler assemblies level the base assembly, and each can include a wheel hub locator that adjustably fixes a hub along a longitudinal horizontal, a vertical, and a lateral horizontal direction. Another embodiment comprises a motorized vehicle undercarriage that carries a frame. The frame has a platform with a top surface defining a plurality of holes in the form of a matrix. Model-making components can be attached and unattached thereto.